The major goal of this pilot, cross-sectional study is primarily to determine the prevalence of exposure to organophosphate pesticides (OPs), and secondarily, to determine the prevalence of neurobehavioral problems in the children of migrant farm workers who live in State of California- run Migrant Housing Centers (MHCs) and whose parents work in surrounding fields during the regular summer agricultural season, April through September. The importance of this study is four-fold: 1) it will establish the prevalence of exposure to OPs in this high risk population; 2) it will use biomarkers (the presence of urinary metabolites of OP exposure); 3) it will investigate the prevalence of neurotoxicity in children, a potentially serious health outcome that may be associated with OP exposure; and 4) it will assess parental occupation as a potential source of exposure for children. The study will examine the relationship between mother's work and exposure and the exposure and neurobehavior of her child Children between the ages of one and five years old living in Migrant Housing Centers in Yolo and Solano counties will be eligible (n=80). Estimates of prevalence of exposure to OPs (as measured by urinary metabolites) and of neurobehavioral problems (as measured by standardized tests) found in children with mothers who currently work in agriculture will be compared to these estimates in children whose mothers are not currently working in agriculture. Our hypothesis is that while all fathers work in the fields and some mothers, it is maternal care that is the major mode of transmission in the age group 1 to 5 years old, Mothers may work in the fields, wash clothes filled with pesticide residue, clean the house filled with pesticide residue and pass this residue to their children. In addition, children will be potentially exposed through residues in house dust and any residential spraying for pests. Bilingual interviewers and psychometric technician will interview parents, collect urine samples from both mothers and children and test children during the summer, in mid-September during peak pesticide (OP) use in California. Urine will be collected from babies by extracting it from disposable diapers or a sterile bag, two appropriate methods for infants. Neurobehavioral testing will consist of standardized tests of cognitive, perceptual and motor functions. If any abnormalities are detected, children will be referred for further medical helps. In addition to urinary assays, Pesticide Use Reports will be collected from Cal-EPA for the geographic areas where parents work and live. The findings from this study have potential significance for establishing the prevalence of exposure to and neurotoxicity of OPs for children who are at high risk. There has been much conjecture about this potential problem, and in order to consider undertaking a larger epidemiologic study, determining baseline prevalence values is essential.